http://hdl.handle.net/1957/8163 2013-05-20T06:24:28Z 2013-05-20T06:24:28Z Cao, Chen http://hdl.handle.net/1957/38561 2013-05-13T18:20:57Z 2013-04-24T00:00:00Z

Helping end-user programmers help themselves : the idea garden approach Cao, Chen End-user programmers face many barriers in programming. Research has seen many programming environments that attempted to lower or remove the barriers but despite these efforts, empirical studies continue to report barriers users face. To investigate this issue, we took a theory-informed approach. Using theories from design, creativity, and problem solving as a lens, we examined end-user programmers' programming obstacles to derive design implications. Synthesizing the implications, we proposed an Idea Garden approach for creating problem-solving support in existing end-user programming environments aimed at helping users help themselves. This approach focuses on delivering problem-solving strategies and programming knowledge in the context of users' work to help them overcome barriers. We developed a proof-of-concept prototype of an Idea Garden for the CoScripter environment. Results from empirical studies of the prototype were encouraging: not only was the Idea Garden able to help users overcome barriers, learn relevant programming and strategies, but such learning persisted with users so that they were able to apply it toward problem-solving new tasks without further help from the Idea Garden. We conclude by providing recommendations to researchers who are interested in developing an Idea Garden for their end-user programming environments. Graduation date: 2013

2013-04-24T00:00:00Z Khormaei, Iranpour http://hdl.handle.net/1957/38548 2013-05-13T15:54:23Z 1989-06-23T00:00:00Z

Improved stability in ACTFEL devices Khormaei, Iranpour The stability of ZnS:Mn AC thin film Electroluminescence (ACEFEL) devices as demonstrated by the brightness-voltage (BV) characteristics is discussed. Two procedures for improvement of the stability are demonstrated. The first method is the addition of a CaS buffer layer to one or both interfaces of the ZnS active phosphor layer. The second method for improving the stability involves a vacuum anneal followed by an oxygen exposure. The oxygen exposure is accomplished by heat treatment of the ZnS surface in air or an oxygen plasma prior to the deposition of the second insulator. A model for the observed instability is proposed in which accumulation of positive charge near the ZnS insulator interfaces gives rise to the observed increase in the BV threshold voltage with aging for the control sample. The positive interface charge is attributed to sulfur vacancies which are positively ionized donors. The improved device stability is attributed to a reduction in the sulfur vacancy concentration in the ZnS concomitant with the addition of a CaS buffer layer or oxygen exposure of the ZnS surface. Graduation date: 1990

1989-06-23T00:00:00Z Hansen, James Edward, 1962- http://hdl.handle.net/1957/38547 2013-05-13T15:47:36Z 1989-06-30T00:00:00Z

A time-multiplexed switched-capacitor circuit for neural network applications Hansen, James Edward, 1962- Analog computation in the form of neural networks is currently receiving much attention. Existing algorithms cannot be easily implemented in hardware because of the large number of neurons needed and the number of connections necessary between them. These problems have motivated development of alternatives to a conventional implementation. Hence, a time-multiplexed switched-capacitor computational block with some neural network characteristics has been developed. The goal of this work is not to exactly model biological neuron qualities but rather to emulate their primary characteristics to the extent necessary to solve some types of problems not suited to digital processing. Graduation date: 1990

1989-06-30T00:00:00Z Xiong, Sicheng http://hdl.handle.net/1957/38533 2013-05-09T17:42:24Z 2013-04-25T00:00:00Z

Active learning of constraints for semi-supervised clustering Xiong, Sicheng Semi-supervised clustering aims to improve clustering performance by considering user supervision in the form of pairwise constraints. In this paper, we study the active learning problem of selecting pairwise must-link and cannot-link constraints for semisupervised clustering. We consider active learning in an iterative manner where in each iteration queries are selected based on the current clustering solution and the existing constraint set. We apply a general framework that builds on the concept of neighborhood, where neighborhoods contain "labeled examples" of different clusters according to the pairwise constraints. Our active learning method expands the neighborhoods by selecting informative points and querying their relationship with the neighborhoods. Under this framework, we build on the classic uncertainty-based principle and present a novel approach for computing the uncertainty associated with each data point. We further introduce a selection criterion that trades-off the amount of uncertainty of each data point with the expected number of queries (the cost) required to resolve this uncertainty. This allows us to select queries that have the highest information rate. We evaluate the proposed method on the benchmark datasets and the results demonstrate consistent and substantial improvements over the current state-of-the-art. Graduation date: 2013

2013-04-25T00:00:00Z